Self-centering susceptor ring assembly

ABSTRACT

A self-centering susceptor ring assembly is provided. The susceptor ring assembly includes a susceptor ring support member and a susceptor ring supported on the susceptor ring support member. The susceptor ring support member includes at least three pins extending upwardly relative to the lower inner surface of the reaction chamber. The susceptor ring includes at least three detents formed in a bottom surface to receive the pins from the susceptor ring support member. The detents are configured to allow the pins to slide therewithin while the susceptor ring thermally expands and contracts, wherein the detents are sized and shaped such that as the susceptor ring thermally expands and contracts the gap between the susceptor ring and the susceptor located within the aperture of the susceptor ring remains substantially uniform about the entire circumference of the susceptor, and thereby maintains the same center axis.

FIELD OF THE INVENTION

This invention is related to semiconductor processing tools, and moreparticularly, to a susceptor ring assembly surrounding a susceptor uponwhich a substrate is located during a semiconductor manufacturingprocess.

BACKGROUND OF THE INVENTION

In the processing of semiconductor devices, such as transistors, diodes,and integrated circuits, a plurality of such devices are typicallyfabricated simultaneously on a thin slice of semiconductor material,termed a substrate, wafer, or workpiece. In one example of asemiconductor processing step during manufacture of such semiconductordevices, the substrate or other workpiece is typically transported intoa reaction chamber in which a thin film, or layer, of a material isdeposited on an exposed surface of the substrate. Once the desiredthickness of the layer of material has been deposited, the substrate maybe further processed within the reaction chamber or transported out ofthe reaction chamber for further processing.

The substrate is typically transferred into the reaction chamber by wayof a wafer handling mechanism. The wafer handling mechanism lifts thesubstrate from a position outside the reaction chamber and inserts thesubstrate into the reaction chamber through a valve or door formed in awall of the reaction chamber. Once the substrate is transferred into thereaction chamber, the substrate is dropped onto a susceptor. After thesubstrate is received on the susceptor, the wafer handling mechanism iswithdrawn from the reaction chamber and the valve is closed such thatprocessing of the substrate can begin. In an embodiment, a susceptorring is located adjacent to, and surrounds, the susceptor upon which thesubstrate is disposed during processing. Such rings can serve tominimize heat loss from the edge of the wafer/susceptor duringprocessing and/or house components such as temperature sensors.

FIGS. 1-3 illustrates a known reaction chamber 10 and substrate supportassembly 12 typically used in the Epsilon® tools produced by ASMAmerica, Inc. of Phoenix, Ariz. The substrate support assembly 12 isconfigured to receive and support a substrate 18 within the reactionchamber 10 when the substrate 18 is being processed. The substratesupport assembly 12 includes a susceptor support member 14 and asusceptor 16. A susceptor ring assembly 20 surrounds the susceptor 16within the reaction chamber 10. The susceptor ring assembly 20 providesa small gap between the inwardly-directed edge of the susceptor ring andthe outwardly-directed edge of the susceptor. The susceptor ringassembly 20 can absorb radiant energy to reduce or eliminate heat lossfrom the outer edge of the susceptor 16 and substrate 18 duringprocessing. The susceptor ring assembly 20 typically used in theEpsilon® tool includes a susceptor ring, which includes a lowersusceptor ring 22 and an upper susceptor ring 24, and a susceptor ringsupport member 26.

During processing of a substrate within a reaction chamber, thetemperature within the reaction chamber varies and may have atemperature range between room temperature and about 1200° C. When thetemperature within the reaction chamber is raised and/or lowered, thevarious components within the reaction chamber thermally expand orcontract accordingly. The commonly known substrate support assembly 12and susceptor ring assembly 20 illustrated in FIGS. 1-3 are locatedwithin the reaction chamber 10 and thermally expand and/or contract asthe temperature within the reaction chamber 10 is raised or lowered. Thesusceptor support member 14 and the susceptor ring support member 26 aretypically formed of an insulating material, e.g., quartz, and thesusceptor 16, lower susceptor ring 22, and upper susceptor ring 24 areformed of a heat-absorbing material, e.g., SiC-coated graphite. Thesusceptor ring support member 26 includes a plurality of pins 28 thatare received by the susceptor ring to positively locate the susceptorring within the reaction chamber 10.

The lower susceptor ring 22, as shown in the bottom plan view of FIG. 3,includes a first aperture 30, a second aperture 32, and a third aperture34 formed therein. The apertures are configured to receive a pin 28 (seeFIG. 1) extending from the susceptor ring support member 26. The firstaperture 30 is located adjacent to the leading edge 36 of the uppersupport ring 24, closest to the gas inlets, and the second and thirdapertures 32, 34 are located adjacent to the trailing edge 38 of theupper support ring 24, closest to the gas exhaust. The first aperture 30is formed as a circular hole through a projection extending from thelower susceptor ring 22. The first aperture 30 is sized to provide asnug fit between the hole and one of the pins 28 extending from thesusceptor ring support member 26. The second aperture 32 is formed as acircular hole that is larger than the outer diameter of the pin 28received therein. The third aperture 34 is formed as an elongated slotconfigured to receive another of the pins 28 therein.

As the temperature increases in the reaction chamber 10 duringprocessing of a substrate 18, the lower and upper susceptor rings 22, 24thermally expand. The susceptor 16, lower susceptor ring 22, and uppersusceptor ring 24 are typically formed of graphite, and the susceptorsupport member 14, susceptor ring support member 26, and pins 28 aretypically formed of quartz. The components (16, 22, and 24) formed ofgraphite have a significantly larger coefficient of thermal expansionrelative to the coefficient of thermal expansion of the components (14,26, and 28) formed of quartz, wherein the graphite components expandmore than the quartz parts in response to the same temperature change.In order to accommodate these differences in thermal expansion, thesecond and third apertures 32, 34 are larger than the corresponding pins28 received therein, the lower and upper susceptor rings 22, 24 are ableto freely thermally expand such that as the susceptor ring expands orcontracts, the pins 28 translate within the second and third apertures32, 34. However, because the first aperture 30 provides a snug fit witha corresponding pin 28, the susceptor ring is prevented from thermallyexpanding away from the susceptor near the leading edge 36 of the uppersusceptor ring 24. The leading portion of the susceptor ring issubstantially pinned relative to the susceptor as the trailing portionof the susceptor ring is free to thermally expand. The lack of movementof the susceptor ring due to thermal expansion near the leading edge ofthe susceptor ring typically reduces the gap between the susceptor ringand the susceptor near the leading edge while the gap between thesusceptor ring and the susceptor near the trailing edge increases.

As a result, the restrained movement of the leading portion of thesusceptor ring relative to the susceptor creates uneven gap spacingbetween the susceptor ring and the susceptor. The uneven gap spacingbetween the susceptor ring and the susceptor at the various locationsabout the susceptor may cause temperature non-uniformities on thesusceptor and the substrate being processed. Further, if the susceptorring is not properly aligned relative to the susceptor, the gap betweenthe susceptor ring and the susceptor may be reduced to the point wherethe susceptor ring contacts the susceptor. Because the susceptortypically rotates about its vertical axis during processing, any contactbetween the susceptor and the ring can create particles that can becomedeposited on the surface of the wafer or other problems with theprocessing of the substrate.

A need therefore exists for a self-centering susceptor ring that iscapable of thermally expanding evenly about a susceptor such that thegap between the susceptor ring and the susceptor expands or contractssubstantially evenly about the susceptor.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a self-centering susceptor ringassembly is provided. The self-centering support ring assembly includesa susceptor ring support member and at least three pins extending fromthe susceptor ring support member. The self-centering support ringassembly also includes a susceptor ring supportable upon the susceptorring support member. The susceptor ring includes at least three detentsformed into a bottom surface of the susceptor ring and an aperturehaving a center point. Each of the detents receives one of the pins ofthe susceptor ring support member. Thermal expansion and contraction ofthe susceptor ring and the susceptor ring support member causes the pinsto slide within the detents such that an edge forming the apertureremains substantially centered about the center point of the apertureduring thermal expansion and contraction of the susceptor ring.

In another aspect of the present invention, a semiconductor processingsystem is provided. The semiconductor processing system includes areaction chamber, a substrate support assembly, and a self-centeringsusceptor ring assembly. The substrate support assembly and theself-centering susceptor ring assembly are located within the reactionchamber. The self-centering susceptor ring assembly includes a susceptorring support member operatively connected to a lower surface of thereaction chamber. The susceptor ring support member includes at leastthree pins protruding away from the lower surface of the reactionchamber. The susceptor ring is supportable on the susceptor ring supportmember. The susceptor ring has at least three detents formed into abottom surface thereof, and each of the detents is configured to receiveone of the pins. The pins are slidable within the detents as thesusceptor ring thermally expands and contracts to maintain the substratesupport assembly centered within the self-centering susceptor ringassembly.

In yet another aspect of the present invention, a self-centeringsusceptor ring assembly for use in a semiconductor processing tool isprovided. The self-centering susceptor ring assembly includes asusceptor ring support having at least three pins extending in the samedirection from at least one side member. Tips of the pins form asubstantially planar support. The self-centering susceptor ring assemblyalso includes a susceptor ring having at least three detents formedtherein for receiving a corresponding pin. During thermal expansion andcontraction of the susceptor ring, thermal expansion or contraction ofthe susceptor ring causes the pins to change relative location withinthe detents to allow the susceptor ring to remain substantially centeredabout a center point.

In accordance with another aspect of the invention, a susceptor ring isprovided for use in a self-centering susceptor ring assembly. Thesusceptor ring includes an upper surface and a lower surface defining athickness therebetween. An aperture is formed through the thickness, andthe aperture has a centerpoint. At least three detents are formed intothe lower surface. The detents are elongated slots aligned radiallyrelative to the center point.

Advantages of the present invention will become more apparent to thoseskilled in the art from the following description of the embodiments ofthe invention which have been shown and described by way ofillustration. As will be realized, the invention is capable of other anddifferent embodiments, and its details are capable of modification invarious respects. Accordingly, the drawing(s) and description are to beregarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a reaction chamber commonly known in theprior art;

FIG. 2 is cross-sectional side view of the reaction chamber shown inFIG. 1;

FIG. 3 is a bottom plan view of a susceptor ring commonly known in theprior art;

FIG. 4 is a cross-sectional side view of a reaction chamber having aself-centering susceptor ring assembly in accordance with an embodiment;

FIG. 5 is a top plan view of the reaction chamber shown in FIG. 4;

FIG. 6A is a top plan view of an embodiment of a susceptor ring supportmember;

FIG. 6B is a side elevational view of the susceptor ring support membershown in FIG. 6A;

FIG. 7A is a bottom isometric view of an exemplary embodiment of asusceptor ring;

FIG. 7B is a bottom plan view of the susceptor ring shown in FIG. 7A;

FIG. 7C is a side elevational view of the susceptor ring shown in FIG.7A;

FIG. 8 is a bottom plan view of an embodiment of a self-centeringsusceptor ring assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 4-5, an embodiment of a reaction chamber 110, asubstrate support assembly 112, and a self-centering susceptor ringassembly 114 of a semiconductor processing system are shown. Thereaction chamber 110 is illustrated as a horizontal flow, cold-wallchamber. It should be understood by one skilled in the art that thereaction chamber is an exemplary embodiment for illustrative purposesonly, and the substrate support assembly 112 and the susceptor ringassembly 114 may be used in other types of semiconductor processingchambers. In an embodiment, the reaction chamber 110 is formed of quartzto allow radiant energy to be transmitted therethrough such that theradiant heat can be absorbed by components of the substrate supportassembly 112 and/or the susceptor ring assembly 114.

The substrate support assembly 112 is located at least partially withinthe reaction chamber 110, as illustrated in FIGS. 4-5. In an embodiment,the substrate support assembly 112 includes a susceptor 116 configuredto receive a substrate 118, a susceptor support member 120, a shaft 122,and a motor (not shown). The motor is located external to the reactionchamber 110 and is operatively connected to the shaft 122. The shaft 122is located within a tube 124 depending from the lower surface of thereaction chamber 110. The susceptor support member 120 is operativelyconnected to the shaft 122 opposite the motor. The susceptor supportmember 120 includes a plurality of feet 126 that are received by thesusceptor 116 to operatively connect the susceptor 116 to the susceptorsupport member 120. In operation, the motor is configured to rotate theshaft 122, thereby causing the susceptor support member 120 and thesusceptor 116 to correspondingly rotate therewith.

As shown in FIGS. 4-5, an embodiment of a self-centering susceptor ringassembly 114 is located within the reaction chamber 110 and surroundsthe substrate support assembly 112. In an embodiment, the susceptor ringassembly 114 includes a susceptor ring support member 128 and asusceptor ring 130 supported on the susceptor ring support member 128.The susceptor ring support member 128 contacts and extends upwardly fromthe lower surface of the reaction chamber 110, and the susceptor ring130 is located on the susceptor ring support member 128 such that thesusceptor ring 130 is disposed about the outer edge of the susceptor 116to assist in compensating for the heat loss from the outer edge of thesusceptor 116 and substrate 118.

In an embodiment, the susceptor ring support member 128 is formed as asubstantially hexagonal member, as shown in FIGS. 6A-B. It should beunderstood by one skilled in the art that the susceptor ring supportmember 128 may also be formed as a square, triangular, rectangular,circular, oval, pentagonal member, or the like. It should also beunderstood by one skilled in the art that the susceptor ring supportmember 128 may be formed with any number of side members 132, whereineach side member has the same or a different length, or the susceptorring support member 128 may be formed having a single side member 132such as circular- or oval-shaped. In an embodiment, the susceptor ringsupport member 128 is formed of a thermally insulating material, such asquartz. In another embodiment, the susceptor ring support member 128 isformed of a thermally absorbing material, such as ceramic-coatedgraphite. It should be understood by one skilled in the art that thesusceptor ring support member 128 can be formed of any material that issubstantially inert with respect to the process gases introduceable intothe reaction chamber 110 during processing of a substrate and issuitable to withstand high temperatures.

The susceptor ring support member 128 also includes a plurality oflocating members 134 attached to the side members 132, as illustrated inFIGS. 6A-6B. In an embodiment, the susceptor ring support member 128includes three locating members 134 spaced about 120° apart relative toeach other. In another embodiment, four locating members 134 are locatedabout 90° apart relative to each other. In a further embodiment, threelocating members 134 are spaced unevenly apart relative to each otherabout the susceptor ring support member 128. It should be understood byone skilled in the art that the susceptor ring support member 128 mayinclude any number of locating members 134 attached thereto, and thelocating members 134 may be spaced apart in any manner relative to eachother. In an embodiment, the locating members 134 are integrally formedwith the side members 132 to form the susceptor ring support member 128.In another embodiment, the locating members 134 are formed separatelyfrom the side members 132 and then operatively attached thereto.

In an embodiment, the locating members 134 extend from the side members132 in a substantially perpendicular manner, as shown in FIGS. 6A-6B.Each locating member 134 extends from both the upper and lower surfacesof the side member 132 to which the locating member 134 is connected.When located within the reaction chamber 110, the lower portion of eachlocating member 134 of the susceptor ring support member 128 is receivedwithin a recess 136 (FIG. 4) formed in the lower surface of the reactionchamber 110. This connection between the susceptor ring support member128 and the reaction chamber 110 prevents rotation or movement of thesusceptor ring support member 128 relative to the reaction chamber 110while providing a stable base upon which the susceptor ring 130 issupported. Each locating member 134 includes an aperture 138 formedthrough the thickness thereof. The aperture 138 is aligned in asubstantially perpendicular manner relative to the plane formed by theside members 132 of the susceptor ring support member 128. The aperture138 maybe a through-hole or a blind hole.

In an embodiment, a pin 140 is inserted into each of the apertures 138formed in the locating members 134, as shown in FIGS. 6A-6B. In anotherembodiment, the pins 140 are integrally formed with the side members 132as a single piece, with or without the locating members 134. In anembodiment, the pin 140 includes a body 142 and a contact member 144,wherein the contact member 144 extends from the body 142. In oneembodiment, at least a portion of the body 142 is inserted into anaperture 138 for assembly such that at least a portion of the body 142and the entire contact member 144 extends from the locating member 134.In another embodiment, the entire body 142 is disposed within anaperture 138 such that at least a portion of the contact member 144extends from the locating member 134. The tip of the contact member 144of each pin 140 is configured to be received by the susceptor ring 130,thereby providing a connection between the susceptor ring support member128 and the susceptor ring 130 (FIG. 4). In an embodiment, the tip ofeach pin 140 extends substantially the same distance above the sidemembers 132 of the susceptor ring support member 128, thereby providinga substantially horizontal planar support upon which the susceptor ring130 is mountable. It should be understood by one skilled in the art thatalthough it is preferred that the tips of the pins 140 provide asubstantially horizontal planar support for the susceptor ring 130, thetips of the pins 140 may also be configured to provide a non-horizontal,or slanted, planar support, or a non-planar support, for the susceptorring 130. In an embodiment, the pins 140 and the contact members 144 areformed of quartz, but it should be understood by one skilled in the artthat the pins 140 and contact members 144 can be formed of any othermaterial substantially inert to the process gases introduced into thereaction chamber. The pins 140 are configured to provide structuralsupport to the susceptor ring 130 while allowing the susceptor ring 130to freely thermally expand and contract.

As illustrated in FIGS. 7A-7C, an embodiment of a susceptor ring 130includes a lower surface 148, a leading edge 150 for placement closestto the chamber's gas inlets, a trailing edge 152 for placement closestto the chamber's gas exhaust, and an aperture 154 formed through thethickness. In an embodiment, the susceptor ring 130 is formed ofgraphite. It should be understood by one skilled in the art that thesusceptor ring 130 may be formed of any material that is inert withrespect to the process gases introduceable into the reaction chamber 110while being capable of absorbing and emitting radiant energy at theelevated temperatures used to process substrates. It should also beunderstood by one skilled in the art that the susceptor ring 130 shownin FIGS. 7A-7B is an exemplary embodiment for ease of reference anddescription thereof, but it should be understood by one skilled in theart that the susceptor ring 130 can be formed of any number of pieces orformed of any type of material suitable for use in processingsubstrates. In the illustrated embodiment, the susceptor ring 130 isformed of a material different from the susceptor ring support member128 such that the coefficient of thermal expansion of the susceptor ring130 is different than the coefficient of thermal expansion of thesusceptor ring support member 128. For example, when the susceptor ring130 is formed of graphite and the susceptor ring support member 128 isformed of quartz, the susceptor ring 130 will expand a greater amountfor a given temperature change relative to the susceptor ring supportmember 128 when heated.

When installed within the reaction chamber 110, as illustrated in FIG.4, the lower surface 148 of the susceptor ring 130 is directed towardthe lower interior surface of the reaction chamber 110, the leading edge150 of the susceptor ring 130 is directed toward the inlet end 156 ofthe reaction chamber 110, and the edge of the susceptor ring 130defining the aperture 154 therein is adjacent to the outer edge of thesusceptor 116. The susceptor ring 130 is configured to absorb radiantheat in the same manner as the susceptor 116 upon which the substrate118 is supported during processing. During processing, the susceptor 116and the substrate 118 tend to lose heat from the outer edges thereof.The susceptor ring 130 is located immediately adjacent to the outer edgeof the susceptor 116 in a spaced-apart manner, thereby preventingcontact between the susceptor 116 and the susceptor ring 130 whilecompensating for a significant portion of the heat loss from the outeredge that the susceptor 116 and substrate 118 would otherwiseexperience. The improved self-centering susceptor ring assembly isconfigured to maintain a substantially even spacing between the aperture154 of the susceptor ring 130 and the outer edge of the susceptor 116while the temperature of the susceptor 116, susceptor ring 130, and thesubstrate 118 change during processing. The spacing allows the susceptor116 to rotate during processing without rubbing and causing particlegeneration.

In an embodiment, the susceptor ring 130 includes three detents 158formed into the lower surface 148, as illustrated in FIGS. 7A-7B. Inanother embodiment, the susceptor ring 130 includes more than threedetents 158 formed into the lower surface 148. Each detent 158 formed inthe susceptor ring 130 is configured to receive a contact member 144 ofa pin 140 extending from a locating member 134 of the susceptor ringsupport member 128 for locating and supporting the susceptor ring 130within the reaction chamber 110. It should be understood by one skilledin the art that the susceptor ring 130 should include a minimum of threedetents 158 formed in the bottom surface to provide a stable connectionbetween the susceptor ring 130 and the susceptor ring support member128.

The susceptor ring support member 128 is configured to support thesusceptor ring 130 at a spaced-apart relationship relative to the lowersurface of the reaction chamber 110 as well as maintain the susceptorring 130 in a substantially fixed location relative to the susceptor116, as illustrated in FIGS. 4-5. The length of the pins 140 extendingfrom the susceptor ring support member 128 provides a pre-determinedspacing between the lower surface of the reaction chamber 110 and theupper surface 146 (FIG. 7C) of the susceptor ring 130. Note that inother arrangements the lower surface need not represent the floor of thereaction chamber. Because the height of the susceptor 116 within thereaction chamber 110 may vary from tool to tool or from model to model,the length of the pins 140 is modifiable to allow the upper surface 146of the susceptor ring 130 to be properly aligned relative to thesusceptor 116. In an embodiment, the pins 140 are removable from theapertures 138 of the locating members 134 of the susceptor ring supportmember 128, thereby allowing the pins 140 to be removed and reworked toprovide a particular spacing between the lower surface of the reactionchamber 110 and the susceptor ring 130. In another embodiment, the pins140 are replaceable such that the pins 140 can be removed and replacedwith pins 140 of a different length, thereby modifying the spacingbetween the lower surface of the reaction chamber 110 and the susceptorring 130.

In an embodiment, each of the detents 158 is formed as an elongatedslot, as shown in FIG. 7B. It should be understood by one skilled in theart that the detents 158 can be formed as any shape sufficient toreceive the tip of a pin 140 extending from the susceptor ring supportmember 128. It should also be understood by one skilled in the art thatall of the detents 158 can be formed as the same shape, at least onedetent 158 may be formed having a different shape than the other detents158, or each detent 158 may be formed as a different shape than all theother detents 158, provided that each of the detents 158 is configuredto allow the pin 140 received therein to translate in a substantiallyradial manner within the detent 158 relative to the center of theaperture 154. In an embodiment, each of the detents 158 extends intoonly a portion of the thickness of the susceptor ring 130, e.g., asblind slots. In another embodiment, each of the detents 158 extendsthrough the entire thickness of the susceptor ring 130, i.e., asthrough-slots. It should be understood by one skilled in the art thatthe detents 158 are configured to receive a pin 140 extending from thesusceptor ring support member 128, wherein the contact member 144 of thepin 140 contacts at least one surface of the corresponding detent 158including the sides and/or the base surface of the detent 158.

In the exemplary embodiment illustrated in FIG. 7B, the detent 158located adjacent to the leading edge 150 of the susceptor ring 130 andis oriented in a substantially radial manner relative to the center ofthe aperture 154 formed in the susceptor ring 130. The detents 158located adjacent to the trailing edge 152 of the susceptor ring 130 areoriented at an angle relative to the detent 158 located adjacent to theleading edge 150 and are likewise oriented in a substantially radialmanner relative to the center of the aperture 154 formed in thesusceptor ring 130. It should be understood by one skilled in the artthat the orientation of the detents 158 relative to each other may varydepending upon the number and location of the detents 158 formed in thesusceptor ring 130, but each detent 158 should be configured to allowthe pin 140 received therein to translate or slide in a substantiallyradial manner within the detent 158 relative to the center of theaperture 154. The detents 158 are configured to receive a pin 140 formaintaining contact between the susceptor ring 130 and the susceptorring support member 128 while allowing the susceptor ring 130 to freelyand substantially uniformly thermally expand and contract as thetemperature of the susceptor ring 130 increases or decreases. Thedetents 158 are generally aligned in a radial manner relative to thecenter point of the aperture 154 formed in the susceptor ring 130.

In an exemplary embodiment, the susceptor ring 130 is formed of graphiteand the susceptor ring support member 128, including the pins 140 andcontact members 144 thereof, is formed of quartz such that thecoefficient of thermal expansion of the susceptor ring 130 is differentthan the coefficient of thermal expansion of the susceptor ring supportmember 128. Graphite components are generally coated with an inertmaterial like SiC or other ceramic, but the graphite tends to dominatethe mass and thus the coefficient of thermal expansion of suchcomponents. As such, as the temperature within the reaction chamber 110increases, the susceptor ring 130 and the susceptor ring support member128 thermally expand, but the susceptor ring 130 thermally expands morethan the susceptor ring support member 128. The thermal expansion of theouter edges of the susceptor ring 130 expands away from the center ofthe aperture 154 while the inner edge defining the aperture 154 expandsinwardly toward the center of the aperture 154. Because the susceptor116 thermally expands within the aperture 154 of the susceptor ring 130in a similar manner, the gap spacing between the outer edge of thesusceptor 116 and the inner surface of the susceptor ring 130 definingthe aperture 154 is reduced. Due to the different coefficients ofthermal expansion between the susceptor ring 130 and the susceptor ringsupport member 128, the susceptor ring 130 tends to thermally expandoutwardly greater than the susceptor ring support member 128.Accordingly, as the susceptor ring 130 thermally expands, the contactmembers 144 of the pins 140 may slide radially inwardly within thecorresponding detent 158 of the susceptor ring 130. The sliding of thecontact members 144 of the susceptor ring support member 128 allows thesusceptor ring 130 to thermally expand while also allowing the aperture154 of the susceptor ring 130 to remain substantially centered about thesusceptor 116. However, if at least one of the detents 158 of thesusceptor ring 130 were not configured to allow the susceptor ring 130to thermally expand in a radial distance greater than the susceptor ringsupport member 128, then the susceptor ring 130 would become off-centerwith respect to the susceptor 116 and the gap between the susceptor ring130 and the susceptor 116 would not be substantially even about theentire outer edge of the susceptor. When the aperture 154 about thesusceptor 116 becomes off-center, the heating profile of the susceptorand substrate 118 becomes uneven, thereby affecting the depositioncharacteristics on the substrate 118.

The self-centering susceptor ring assembly 114 is centered about thesubstrate support assembly 112 within the reaction chamber 110. Thesusceptor ring support member 128 operatively connects the susceptorring 130 to the reaction chamber 110 while also supporting the susceptorring 130 in a spaced-apart relationship relative to the susceptor 116.As the temperature within the reaction chamber 110 increases ordecreases, the susceptor ring 130 thermally expands or contractsrelative to the susceptor 116. The connection between the pins 140 ofthe susceptor ring support member 128 and the corresponding detentsformed in the susceptor ring 130 allow the susceptor ring 130 tothermally expand or contract relative to the susceptor 116 such that thegap between the susceptor 116 and the susceptor ring 130 remainssubstantially even. Each pin 140 is free to slide within a correspondingdetent 158 as the susceptor ring 130 expands or contracts more than thesusceptor ring support member 128, wherein the pins 140 slide in aradial manner relative to the center point of the susceptor 116 toensure substantially even radial expansion of the susceptor ring 130relative to the center of the susceptor 116. It should be understood byone skilled in the art that each pin 140 is independently slidablewithin the corresponding detent 158 to allow thermal expansion of thelocalized portion of the susceptor ring 130 around the detent 158.Although the above description indicates that the pins 140 slide withinthe detents 158, it should be understood by one skilled in the art thatit is the increased radially outward thermal expansion of the susceptorring 130 relative to the susceptor ring support member 128 that causesthe pins 140 to slide within the detents 158. In other words, eventhough both the susceptor ring 130 and the susceptor ring support member128 are both thermally expanding radially outward, the susceptor ring130 is thermally expanding at a faster and greater rate such that thesusceptor ring 130 is sliding past the pins 140 of the susceptor ringsupport member 128, wherein the relative location of the pins 140 withinthe detents 158 changes and such change in position is accomplished bythe pins 140 sliding within the detents 158 or the detents 158 slidingrelative to the pins 140.

While preferred embodiments of the present invention have beendescribed, it should be understood that the present invention is not solimited and modifications may be made without departing from the presentinvention. The scope of the present invention is defined by the appendedclaims, and all devices, process, and methods that come within themeaning of the claims, either literally or by equivalence, are intendedto be embraced therein.

1. A self-centering susceptor ring assembly comprising: a susceptor ringsupport member and at least three pins extending from said susceptorring support member; and a susceptor ring supportable upon saidsusceptor ring support member, said susceptor ring including at leastthree detents formed into a bottom surface of said susceptor ring and anaperture having a center point, wherein each of said detents receivesone of said at least three pins; wherein thermal expansion andcontraction of said susceptor ring and said susceptor ring supportmember causes said pins to slide within said detents such that an edgeforming said aperture remains substantially centered about said centerpoint of said aperture during thermal expansion and contraction of saidsusceptor ring.
 2. The self-centering susceptor ring assembly of claim1, wherein said detents are formed as elongated slots.
 3. Theself-centering susceptor ring assembly of claim 2, wherein saidelongated detents are oriented in a substantially radial manner relativeto said center point of said aperture.
 4. The self-centering susceptorring assembly of claim 1, wherein said detents are formed through only aportion of a thickness of said susceptor ring.
 5. The self-centeringsusceptor ring assembly of claim 1, wherein said susceptor ring isformed of graphite and said susceptor ring support member is formed ofquartz.
 6. The self-centering susceptor ring assembly of claim 1,wherein said susceptor ring support member is formed of a differentmaterial than said susceptor ring.
 7. The self-centering susceptor ringassembly of claim 1, wherein said aperture is configured to surround asusceptor, and said edge forming said aperture is spaced-apart from anouter edge of said susceptor to form a gap therebetween.
 8. Theself-centering susceptor ring assembly of claim 7, wherein said gapremains substantially even between said susceptor ring and saidsusceptor when said susceptor ring and said susceptor ring supportmember thermally expand and contract.
 9. A semiconductor processingsystem comprising: a reaction chamber; a substrate support assemblylocated at least partially within said reaction chamber; and aself-centering susceptor ring assembly located within said reactionchamber, said self-centering susceptor ring assembly comprising: asusceptor ring support member operatively connected to a lower surfaceof said reaction chamber, said susceptor ring support member includingat least three pins protruding away from said lower surface of saidreaction chamber; and a susceptor ring being supportable on saidsusceptor ring support member, said susceptor ring having at least threedetents formed into a bottom surface of said susceptor ring and each ofsaid detents configured to receive one of said at least three pins,wherein said pins are slidable within said detents as said susceptorring and said susceptor ring support member thermally expand andcontract to maintain said substrate support assembly centered withinsaid self-centering susceptor ring assembly.
 10. The semiconductorprocessing system of claim 9, wherein said susceptor ring and saidsusceptor ring support member are formed of dissimilar materials. 11.The semiconductor processing system of claim 9, wherein said detentsform a radial pathway relative to a center point of said substratesupport assembly.
 12. The semiconductor processing system of claim 9,wherein each of said pins is independently slidable during thermalexpansion and contraction of said susceptor ring.
 13. A self-centeringsusceptor ring assembly for use in a semiconductor processing toolcomprising: a susceptor ring support having at least three pinsextending in the same direction from at least one side member, wherein atip of each of said at least three pins form a substantially planarsupport; a susceptor ring having at least three detents formed thereinfor receiving said at least three pins such that during thermalexpansion and contraction of said susceptor ring, thermal expansion orcontraction of said susceptor ring causes said pins to change relativelocation within said detents to allow said susceptor ring to remainsubstantially centered about a center point.
 14. The self-centeringsusceptor ring assembly of claim 13, wherein said detents are formed aselongated slots.
 15. The self-centering susceptor ring assembly of claim14, wherein said detents are aligned in a radial manner relative to saidcenter point.
 16. The self-centering susceptor ring assembly of claim13, wherein said susceptor ring includes an aperture formed therein,said aperture configured to surround a susceptor, thereby providing asubstantially uniform gap between an edge of said susceptor ringdefining said aperture and said susceptor.
 17. The self-centeringsusceptor ring assembly of claim 16, wherein said change in relativelocation of said pins within said detents during thermal expansion andcontraction of said susceptor ring causes said gap between said edge ofsaid susceptor ring defining said aperture and said susceptor to remainsubstantially uniform.
 18. A susceptor ring for use in a self-centeringsusceptor ring assembly comprising: an upper surface and a lower surfacedefining a thickness therebetween; an aperture formed through saidthickness, said aperture having a center point; at least three detentsformed into the lower surface, wherein said detents are elongated slotsaligned radially relative to said center point.
 19. The susceptor ringof claim 18, wherein said detents are evenly spaced about said aperture.20. The susceptor ring of claim 18, wherein said detents are unevenlyspaced about said aperture.
 21. The susceptor ring of claim 18 furthercomprising more than three detents formed into the lower surface. 22.The susceptor ring of claim 18, wherein each of said at least threedetents are formed through only a portion of said thickness.
 23. Thesusceptor ring of claim 18, wherein at least one of said at least threedetents is formed through the entire thickness.